"These include both domestic and international terrorism matters and consist of a variety of preventive actions, including arrests, seizure of funds and disruption of terrorist recruiting and training efforts and even, in certain cases, the prevention of actual attacks," said Larry Mefford, assistant director of counterterrorism for the FBI. He was testifying Thursday before a Senate judiciary subcommittee.

FBI officials declined to offer more details about the incidents.

Mefford said that investigations are ongoing in about 40 states against what he called al Qaeda "members and their affiliates." Previously, government sources have said several hundred people in the country are under surveillance as suspected operatives or sympathizers.

Not only are FBI agents looking for operatives but they also are trying to locate anyone helping such people with fundraising, recruiting, training or other logistical efforts, Mefford said.

"We are also concerned about al Qaeda's continued intention and efforts to recruit U.S. citizens to support their cause," he added.

While some experts have warned they believe the organization can mount only smaller attacks in the wake of the global effort to disrupt it, "We remain ... concerned that al Qaeda's intention to launch another major attack inside the U.S. continues," Mefford said.

He also told the panel that the bureau does not have information identifying specific targets and said that attacks could take many forms. Because of that concern, FBI officials say their first priority is to root out any al Qaeda members operating inside the United States.

"This is particularly challenging, given that the identities of U.S.-based al Qaeda sleeper cells are probably the closest-held secrets in their networks," Mefford said.

At the same hearing, David Aufhauser, the general counsel at the Treasury Department, said that "in many cases" Saudi Arabia is the "epicenter" for the trail of money used in global terrorism. Some of that money goes to al Qaeda, he said.

Asked by Sen. Jon Kyl, R-Arizona, if money from Saudi Arabia is a "significant source of funding for terrorism generally," the Treasury official replied, "Yes, principally al Qaeda but many other recipients, as well."

Mefford told the panel that al Qaeda operational commander Mohammed Atef was killed in an early 2002 bombing raid in Afghanistan. It was the first time that a U.S. official has said publicly that Atef was killed.

The FBI still lists his name and picture as one of the 22 Most Wanted Terrorists, without any indication suggesting he is dead.